Clean up lockutils logging

As discussed in [1], the logging in lockutils is not ideal, both
in terms of clarity and volume.  This change removes some
redundant or just plain unnecessary log messages, while improving
the remaining ones to provide more detail to help debugging
contention issues.  Specifically, it:

 * Adds timing information to external lock messages, similar
   to what was already added for internal locks.
 * Removes a now-unnecessary 'attempting' message that was only
   useful for determining the timing info now included in the log
   message itself.
 * Removes a "released and closed" log message that isn't really
   interesting since it happens after the file was unlocked, and
   only tells us that the file was closed normally, when we would
   only care if that step failed for some reason (which will still
   be logged).
 * Removes the logging in internal_lock that was primarily added
   to debug a phantom problem with eventlet semaphores.
 * Adds a parameter to the lock() context that tells it whether
   to log its debug messages.  This allows synchronized to not
   log duplicate messages when it acquires a lock.

Changes for more intelligent logging, such as only logging when
contention occurs as opposed always, are left as a future
enhancement.

[1]: http://lists.openstack.org/pipermail/openstack-dev/2014-September/047181.html

Partial-Bug: 1374075
Change-Id: I7bb36cdbb2e0f1643e1499054433894142cd2ee3
Merge "Clean up lockutils logging"